Pain management strategies in the dental patient

The identification of acute and chronic pain in the dental patient is problematic in both the feline and canine species.

The only reliable marker for pain recognition is behavior. One has to take the anthropomorphic approach when dealing with a possible painful situation.

•Assumptions:

Dental manipulation causes pain.The transmission of pain impulses occurs in the anesthetized patient, and the electrochemical footprint causes post-operative pain.

Chronic pathological situations result in pain.

The perception of pain in animals is no different than in human beings.

The manifestation of pain in animals is masked due to human conditioning and genetic programming.

The neurochemical activity at the brainstem is similar to that at the dorsal horn of the spinal cord.

That pain control is being effectively managed with presently available pharmacologic and adjunctive techniques due to the paucity of pharmacokinetic data.

Therapeutic strategies in dental pain management:

• Pre-emptive pain management is mandatory.

• The best pain management uses the multimodal therapeutic regimen employing drug synergism and facilitating the interruption of the nociceptive pathway at several levels.

• The use of local and regional analgesics to block the transmission of noxious stimuli at the point of origin is pivotal in managing surgical pain.

• To obtund or abolish the wind-up phenomenon in cases such as oral tumors and gingivostomatitis.

An important component of perioperative pain management is the use of species-specific pain cocktails. These cocktails are administered by constant rate infusions. In feline patients, the low-dose administration of ketamine and butorphanol or buprenorphine is suitable, whereas in the dog, a morphine, ketamine and lidocaine cocktail is preferred.

Ketamine is thought of as a chemical restraint agent and dissociative anesthetic but may play an important role in oral pain management. This drug can block specific receptors in the brain stem and help prevent central hypersensitization and "windup," a phenomenon that occurs when the brain stem is bombarded with stimuli from sites of tissue injury originating around the head.

There are obstacles to providing routine and effective analgesia that is specific to the cat.

• 1. The difficulty in recognizing and assessing oral pain in cats.

• 2. Choosing suitable analgesic agents with no unwanted side effects.

Because cats have some unique features that impact on pharmacokinetics and pharmacodynamics (e.g., relative deficiencies in hepatic glucuronide conjugation, sensitivity of hemoglobin to oxidative injury, and perhaps different populations and distribution of opiod receptors), it is not prudent to extrapolate to this species. The oral pH facilitates the use of transmucosal application of buprenorphine for pain management in this species.

Local injectable pain cocktails, e.g. morphine /lidocaine, bupivicaine/lidocaine/morphine, bupivicaine/lidocaine/buprenorphine are useful in reducing drug toxicity due to the dilution factor, speeding up the response time and blocking the opoid receptors at the site of injection.

•Local & regional nerve blocks:

Intraosseous anesthesia involves the injection of anesthetic solution directly into the cancellous bone proximate to the cortical plate or into the periodontal ligament with resultant spread to the cancellous space.

•Periodontal ligament blocks

Periodontal ligament infiltration provides excellent anesthesia but is limited in its application to the anterior teeth, the canine tooth in the cat and the canine and incisor teeth in the dog.

It is of particular benefit in young animals and is uniquely suited for single- tooth anesthetic requirements.

•Intraosseous anesthesia

The intraosseous route of delivering anesthetics for dental procedures has been in use in human dentistry for some time. However, there have been no reports of its use in the Veterinary dental patient. This method of administering anesthesia shares similar indications with the periodontal ligament anesthesia and can be used in periodontitis cases.

The advantages of intraosseous anesthesia are:

• Instant anesthesia without the post-op complication of paresthesia.

• Regional analgesia without soft-tissue cytotoxicity.

• The injection site is available for additional anesthetic administration should the need arise.

• Less technique sensitive than periodontal ligament anesthesia.

• Requires a lower total anesthetic dosage.

Equipment needed

• X-tips (available from Tulsa Dental).

• Latch-type hand piece capable of 15,000-20,000 rpm.

• Air driven or electric dental unit.

Method of administration

• Obtain a set of preoperative radiographs.

• Identify the tooth or area to be operated (inject distal to this area).

• Inject a small amount of local anesthetic in the buccal mucosa at the site where the drill will enter.

• Attach the drill sleeve and guide to the latch-type, slow-speed handpiece.

• Place the tip firmly against the buccal alveolar bone before starting to drill.

• You will feel the drill enter the cortex after going through the buccal plate.

• Use a hemostat or needle holder to grasp the guide sleeve.

• Remove the drill leaving the guide sleeve in the bone.

•Local analgesia

Local anesthetics block the transmission of pain to the brain stem. All other products modulate pain sensation only.

The mechanism of action of local anesthetics prevents the influx of sodium ions into the nerve axon. The loss of sensation is complete when properly administered. The duration of analgesia depends on your choice of product.

Agent, relative potency, onset of action, duration of effect (mins):

• Bupivicaine, 8, intermediate, 180-600, (2-10 mins).

• Mepivicaine, 2, fast, 120-240, (1-4 mins).

• Lidocaine, 2, fast, 90-200, (1-4) mins.

•Regional anesthesia

The indications for regional anesthesia include: Tumor resections, oral trauma involving fractures of teeth and bones, and lacerations of soft tissue requiring surgical intervention, severe periodontal disease needing advanced surgical procedures, gingivostomatitis, tooth extractions and endodontic repair.

•Mandibular nerve block:

Supplies all the teeth in the mandible the gingiva, mucosa and lower lip. The nerve enters the mandibular alveolar foramen, courses the mandibular canal and exits via the caudal middle and rostral mental nerves.

To block the mandibular nerve for dental procedures, the foramen is palpated and local anesthetic is injected by way of an Intraoral or extroral route. The foramen is located on the lingual aspect of the caudal mandible. The oblique line that connects the distal cusp of the first molar in the cat, third molar in the dog, and the angular process crosses the foramen. In most normal-sized animals, the foramen is located 0.5-1cm from the ventral border of the mandible.

•Maxillary nerve block

In the cat, the rostral maxillary nerve branches off the maxillary before it enters the infraorbital canal. It then enters the incisivomaxillary canal on the orbital floor and courses medially and dorsally to supply innervation to the premolars canine and incisor teeth. The middle and caudal maxillary alveolar nerves enter the maxilla on the ventral floor of the orbit and innervate the molar and premolar teeth. To adequately block these nerves, the anesthetic needs to be introduced in the rostroventral aspect of the orbit, with an approach from the ventral orbital rim or by way of deep infiltration into the infraorbital canal. In the dog, infiltration within the infraorbital canal blocks these three branches of the maxillary nerve supplying the maxillary dentition. Blocking the infraorbital nerve as it exits the infraorbital canal in both the dog and the cat does not provide analgesia for the premolars canine or incisor teeth.

•Opiods

The opiods as a group are excellent analgesics without the undesirable side effects seen with NSAIDs. Morphine, oxymorphone, hydromorphone, fentanyl, butorphanol and buprenorphine are the frequently used opiods

Butorphanol is widely used, but it has a ceiling effect and requires frequent dosing. It can be combined with ketamine in the CRI perioperative cocktail. The dosage is 12 mg butorphanol in 1 liter of LRS given at 1-2 ml/kg/hr.

Butorphanol will antagonize the sedative effect of high doses of a complete opiod agonist.

In cats, the analgesic effect of butorphanol and oxymorphone combined is greater than the additive effect. Another option is the low dose administration of butorphanol in Pet-tinic, clindamycin liquid or amoxicillin. Either the 2 mg /ml or 10 mg /ml preparation can be used to make a final concentration of 0.46 to 0.49 mg/ml of butorphanol. This is dosed at 0.5 ml-1.0 ml for a 1- 20 lb. cat twice daily.

•Fentanyl:

The transdermal 25, 50 and 100 ug/hr patches have a lag time of approximately 12 hours. It's a novel "non-intrusive" method of administering the product. There is evidence that the uptake is unpredictable, and the plasma concentration is variable among cats.

Buprenorphine would appear to be the opoid of choice for pain attenuation in the cat. The onset of action is relatively slow (20-30 minutes); its duration of effect lasts from eight to 12 hours. The buccal or transmucosal route has proved to be ideal for cats.

Tramadol is an effective and well-tolerated agent to reduce pain resulting from trauma, and also for the management of chronic pain of malignant or nonmalignant origin.

The combination of tramadol and morphine is infra-additive and thus not recommended for post-operative analgesia.

The administration of tramadol and an NSAID provides more profound analgesia than either drug used alone.

•NSAIDS:

NSAIDs are contraindicated in animals with pre-existing renal disease, hypovolemia or bleeding disorders. NSAIDs, by controlling inflammation, help prevent central hypersentization or wind-up. The available NSAIDs are: meloxicam, piroxicam, carprofen, ketoprofen and tepoxalin.

Pain control is an unimplemented and underutilized medical need for our veterinary dental patients. In order to institute adequate pain management strategies, a multidisciplinary, multimodal approach should be taken.

Dr. Surgeon owns the ANC Veterinary Center in New Rochelle, New York. He is a fellow of the Academy of Veterinary Dentistry and a diplomate of the American Veterinary Dental College.